Today with the development in wireless communications, various functions such as sending/receiving text messages, saving telephone numbers, wireless Internet access, etc. are added to the functions of a cell phone, i.e., a mobile phone terminal, in addition to the simple voice conversation function. Accordingly, there is an increasing need for inputting letters, but there is a problem that it is difficult to make a large input device for a handheld device small in size. Therefore, there has been a need for a method of inputting letters while not significantly modifying the size of the input device and using a conventional keypad with 3×4 numeric keys or buttons without modification. With emerging of small or reduced devices such as PDA (Personal Digital Assistance) having a function of editing documents or tables which is possible with a large apparatus like a conventional desktop computer, there is an increasing need for an apparatus small in size but allowing alphabets to be input.
In order to input alphabets with a typical reduced or small keypad, a method of inputting English alphabets using the keypad generally employed is to fixedly allocate two or three English alphabets onto each numeric button on the numeric keypad, as shown in FIG. 1. For example, if a user intends to input alphabets of “mobile”, he has to press a button for transferring the node into an English input mode and then No. 6 button (“m” is displayed). He then has to press a separate button for ending alphabet input, No. 6 and then No. 3 button (“o” is displayed) and then the button for ending alphabet input, . . . and he has to continue to press buttons for the procedure. According to the aforementioned method, it is seen that the number of button presses in order to input six alphabets is very large and there is also not a given pattern in the operation of button press. Such an input method is not easy to use although a user memorizes the keypad number arrangement, and even annoys a beginner.
There have been proposals in order to achieve easy and rapid alphabet input by improving the conventional button number fixed alphabet allocation method. An example of the proposals is the Graffiti(trademark) method widely used in PDA devices such as Palm Tungsten Ts(trademark) (see http://palmone.com). The Graffiti method provides a separate input window in addition to a display screen on a PDA. When a user writes alphabet shapes according to a predetermined rule on the input window with, for example, a pen as if she/he takes a handwriting note, corresponding alphabets interpreted through a writing recognition program are displayed on the display screen. However, since every person has a different writing style, the alphabet recognition ratio is low and its speed is also slow, not satisfying people who are accustomed to a speedy keyboard input manner.
In addition, there is a method of inputting alphabets by means of a keypad used in BlackBerry(trademark) (see http://blackberry.com for more details), FASTAP(trademark) (see http://digitwireless.com for more details) and Treo 600(trademark) (see http://handspring.ccm for more details). The apparatuses provide compact keypads to allow a user to input alphabets in consumer electronics such as a small cell phone or PDA. In such a small keypad conventionally proposed, since relatively many buttons are densely arranged in a narrow space, it is not easy to use fingers in button operation (e.g. pressing the button). Another problem is that the user has to press small buttons one by one arranged in the narrow space to input alphabets, using an auxiliary device similar to a pen. Also, according to the method, the 3×4 button numeric keypad used in a conventional cell phone cannot be used without modification. In addition, the conventional modified small keypad for inputting alphabets are produced in different shapes depending on manufacturers and thus could be easily unified or standardized.
Therefore, there has been a need for technology that can implement new and easy alphabet input for which the conventional keypad is not significantly modified and the keyboards are thus easily unified.